<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        #box{width: 100px;height:100px;background: red}
    </style>
</head>
<body>
    <!-- <标签名 行为属性="要执行的js代码"></标签名> -->
    <div id="box" onclick="alert('hello world123')"></div>
</body>
</html>